Want to hear a Silicon Valley joke? Two geek billionaires walk into a coffee shop and nobody notices.

There’s no punchline. This actually happened a couple of weeks ago when I was in Mountain View and the co-founders of WhatsApp popped into their local for a brew. Despite being full of start-ups, nobody in the Red Rock Café seemed to recognise the pair who had just sold their app to Facebook for upwards of $16bn.

WhatsApp has almost 500 million active users around the world but many in Silicon Valley’s elite only discovered the chat app when Mark Zuckerberg opened his chequebook. It’s entirely possible that, in the past year, more people here have tried Google Glass, the sci-fi headset that most outside Silicon Valley love to hate, than sent a message on WhatsApp.

With oodles of funding and technical talent, this is still the best place on earth to build a tech company. Not so long ago, that also meant that whatever people here used with their friends tended to become the next big thing.

But as San Francisco becomes a one-horse town, it risks becoming detached from mainstream tastes. A consumer app that catches fire with normal folks can be completely ignored here, while things that get the uber-geeks excited don’t always transfer to the outside world. Pinterest is an example of this. Millions of Midwestern moms signed up to the online scrapbooking service long before the geeks had heard of it.

But in 2012, around the same time as Pinterest moved to San Francisco, the hot local app was Path. A mobile social network founded by a former Facebook executive, it is a beautiful and useful app. But being Silicon Valley’s darling did not help Path to reach the masses, who were soon to fall for something quite different: Snapchat. While filling a similar need – sharing photos on the go – Snapchat is as inelegant and fast as Path is well-crafted and considered.

Though now hyped to the hilt, Snapchat was propelled to popularity by high-school kids. The messaging app is based not in Silicon Valley but in Los Angeles, and its recent recruitment video touted the benefits of being out there in the real world “as opposed to being stuck in this bubble”.

Now that so many of us own smartphones, a small clique of geeks can no longer dictate which apps are worth a billion dollars.